Escapement for a time rate mechanism



J- A- REINHARDT ESCAPEMENT FOR A TIME RATE MECHANISM Jan. 23, 1962 Filed July 28, 1958 United States Patent ESCAPEMENT FOR A TIME RATE MECHANISM Joseph A. Reinhardt, Wheaton, Ill., assignor, by mesne assignments, to the United States of Americaas represented by the United States Atomic Energy Commission Filed July 28, 1958, Ser. No. 751,237 1 Claim. (Cl. 58-116) This invention relates to a clock work escapement. In particular it has reference to improvements in a cylinder escapement, sometimes termed the Graham horizontal escapement.

A principal object of the invention is to provide an escapement which is practically unaffected by variations in the applied torque whereby to obtain isochronism of a degree incapable of attainment in other types.

Another object resides in providing an isochronous escapement of rugged character enabling the same to be used in connection with moving objects presenting a vibratory environment.

A further object resides in providing an escapement of the class mentioned including means for rapidly ad justing the rate.

Still another object is to provide an escapement as aforesaid in which the teeth of the escape wheel are of a simple configuration devoid of functionally critical, acutely angled corners enabling manufacture thereof at comparatively low cost.

A further object is to provide an escapement in which oscillation of the lever is derived from a torsion spring which is readily reproducible in quantity production thereby to eliminate the need for extensive adjustment of the mechanism as is often necessary with escapements of other current types.

Broadly regarded the invention mechanism comprises an escape wheel which is arranged to be driven by a source of power and is cooperative with a pallet of segmental, hollow, cylindrical form carried at the'end of a torsion spring. The teeth of the escape wheel are best described as spatulate, the radially disposed sides whereof cooperate with the active faces of the pallet. By shaping the teeth and the pallet in accordance with the principles of the invention, i.e. assuring a minimum amount of frictional contact and a maximum of rolling contact between the pallet and teeth isochronism may be almost ideally realized. Oscillation of the pallet at its predetermined rate is through the medium of a straight torsion spring having its axis of twist coaxial to the pallet. Adjustment of the period of oscillation is accomplished by mounting the pallet at the center of an arm having adiustable masses at the ends thereof.

The invention will be more fully understood from the following description which, taken with the accompanying drawings, illustrates a preferred form in which the same may be embodied in practice.

In this drawing:

FIG. 1 is a perspective view of an escapement in accordance with the invention;

FIG. 2 is a detail of the escape wheel and pallet, in one position of the pallet;

FIG. 3 is a partial view similar to FIG. 2 but showing another position of the pallet;

FIG. 4 is a side elevation of the pallet; and

FIG. 5 is a detail view taken in the direction of the line 5-5 of FIG. 4.

Turning now to the drawing, energy is imparted to the escape Wheel through a pinion 11 forming part of a gear train to the source of power, there being a common arbor 12 journalled in suitable bearings.

The escape wheel is provided with any suitable number of peripheral teeth 16 of spatulate form extending from a base circle indicated at 20. Rotation is as indicated by the arrow. The leading face A of a tooth is in alignment with a tangent to a base circle of radius B concentric with the axis of rotation C of the wheel. The outer surface D of the tooth is an arc of radius E struck from a center F displaced to the right of the axis C by an amount G and below that axis by an amount H. The peripheral extent of the tooth is fixed by striking an arc J from a center K which lies at one end of the outer diameter L of the wheel. It will be apparent from FIG. 2 that the radius B, being less than the radius L/ 2 will conform the outer edge of the tooth so that the leading corner lies radially Within the outer or trailing corner. In one practical embodiment of the invention the dimensions aforesaid are as follows:

Arranged to cooperate with the escape wheel is the pallet 21 (shown enlarged in FIGS. 4 and 5) which is essentially a barrel-like member comprising a hollow cylindrical body 22 having a bearing stud 23 at the upper end thereof and inner and outer diameters V and W respectively. The body 22 is longitudinally truncated along a portion thereof to define a pair of pallet surfaces 24 and 25 coactive with the teeth 16 in a manner to be detailed. The pallet 21 oscillates on an axis N spaced at a distance P from the axis C of the escape wheel. In the sample dimension P=0.6609".

In order that the greatest possible degree of rolling contact may be achieved between the pallet surface 24 and the surface A of a tooth, the pallet surface is comprised of two merging arcs, one of radius R and the other of radius S, tangent to each other and to a chord spaced at a distance T from the diameter. Radius S is also tangent to the circle of radius V. Radius R is struck from a center displaced a distance U from the center N. In the example, referred to hereinabove, the dimensions of the pallet are as follows:

The radius R, together with the rounded corner S are substantially an involute so that during contact of the pallet surfaces with the cooperative edges of the teeth rolling contact is provided, or at least a minimum amount of sliding contact.

A cylindrical support 31 is carried on the main framework 30 of the mechanism with which the invention is incorporated and includes a bearing 32 at its lower end having a bore 33 to receive the boss 23 of the pallet 21 for oscillation therein. At its upper end a cap 34 secured to the support 31 anchors one end of a torsion spring 36 which latter is similarly secured at its lower end in a bore 37 of the pallet 21. The spring 36 may be attached by any recognized technique, e.g. low temperature brazing or soldering.

A stud 41 formed on one side of a boss 42 is received in a bearing (not shown) and the boss is secured in the aperture 44 of the pallet 21. Thus bearings for the pallet are provided on both ends thereof.

A horizontally oscillatable pendulum providing impulsing of the escape wheel is constituted as a pair of arms 46 formed in common and afiixed to the boss 42.

Adjustment of the period of .oscillation is accomplished by means of weights 418 screw-threadedly engaged on the distal ends of the arms 46. To facilitate adjustment the weights are provided with screw-driver slots 49 and radial, partial slits 51 whereby, following adjustment the weights may be pinched and locked in their set positions against dislodgment under vibration.

Operation is as follows: Assuming an initial starting impulse applied to the arms 46 the pallet is oscillated on its axis against the bias of the spring 3 6 which thereafter applies a restoring couple to maintain oscillation of the pallet, the friction loss being made up by energy supplied through the escape wheel.

While the action of the escape wheel and pallet is, in a basic sense, that of the Graham escapement the invention possesses advantages not inherent in the classical Graham arrangement. By employing a torsion spring the beat rate of the escapement is practically completely insensitive to alterations in torque and virtually ideal isochronism is realized. Also, by providing the novel pallet working faces engagement thereof with the escape wheel teeth is, to the greatest possible extent consistent with other considerations, more of a rolling, than a sliding character, thereby resulting in substantial reduction of friction and consequent contribution to isochronism.

Two positions of the pallet are seen in FIGS. 2 and 3. It will be noted that, as the pallet rotates clockwise from the wheel-locking position of FIG. 2 to release the tooth there shown in engagement, the curved surface of the pallet face 24 will roll on the surface A. As the pallet escapes from the tooth the surface D of the tooth slides thereagainst, the eccentric curvature whereof is adapted to minimize resistance by camming the pallet away from its locking position, and such position obtains until the pallet moves into the position of FIG. 3. It Will be observed that the pallet position of FIG. 2 is not necessarily the extreme counterclockwise position. In use slight variations in the extent of abutment of the pallet and teeth will occur due to vibration, variable friction and other factors. However, as averaged over a period of time the fullest possible advantage of the invention organization may be realized.

While I have shown a certain embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made and I therefore contemplate by the appended claim to cover any such modifications as fall within the true spirit and scope of my invention.

I claim:

An isochronous escapement comprising a framework, an escape wheel mounted for rotation on said framework, means providing input energy to said wheel, said wheel having a plurality of spatulate teeth peripherally thereof, each tooth having a straight leading edge lying on a tangent to a base circle concentric with the rotational axis of the wheel and of less diameter than the base circle of the teeth, a member supported for oscillatory motion on said framework for intermittent looking relalarger radius being struck from a common center and disposed adjacent the outer periphery of the member and the portions of smaller radius merging therewith and being disposed adjacent the inner periphery of the memher, and resiliently deformable means secured between the member and framework for restoring the member after each excursion thereof.

References Cited in the file of this patent UNITED STATES PATENTS 9,310 Terry Oct. 5, 1852 46,576 Mozart Feb. 28, 1865 2,196,866 Juillerat Apr. 9, 1940 2,725,716 Varaud Dec. 6, 1955 FOREIGN PATENTS 496,164

Great Britain Nov. 25, 1938 

